Apparatus for detecting or monitoring for a chemical precursor in a high temperature environment

ABSTRACT

An apparatus and method are disclosed for monitoring and/or detecting concentrations of a chemical precursor in a reaction chamber. The apparatus and method have an advantage of operating in a high temperature environment. An optical emissions spectrometer (OES) is coupled to a gas source, such as a solid source vessel, in order to monitor or detect an output of the chemical precursor to the reaction chamber. Alternatively, a small sample of precursor can be periodically monitored flowing into the OES and into a vacuum pump, thus bypassing the reaction chamber.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.62/634,793 entitled “APPARATUS FOR DETECTING OR MONITORING FOR ACHEMICAL PRECURSOR IN A HIGH TEMPERATURE ENVIRONMENT” and filed on Feb.23, 2018, the disclosure of which is hereby incorporated herein forreference.

FIELD OF INVENTION

The present disclosure generally relates to an apparatus for forming afilm on a semiconductor substrate. Specifically, the present disclosurerelates to a chemical source for the apparatus and detecting ormonitoring a concentration of a gas provided by the chemical source.

BACKGROUND OF THE DISCLOSURE

Chemical Vapor Deposition (CVD) and Atomic Layer Deposition (ALD) areboth processes used to form a film on a semiconductor substrate disposedwithin a reaction chamber. The processes may involve flow of a first gasonto the substrate and flow of a second gas onto the substrate, suchthat the first gas reacts with the second gas in order to form a filmhaving a particular chemical composition on the semiconductor substrate.

The chemistries used for these processes generally are kept inparticular conditions in order to ensure proper film formation and toavoid any defects or clogging issues. Defects may occur due tocondensation of heated chemistries along a gas pathway to the reactionchamber. The condensation of the heated chemistries may lead to achemical reaction within the gas pathway prior to reaching the reactionchamber, leading to adverse particle formation on the film formed withinthe reaction chamber.

In addition, clogging may occur within the gas pathways due to thecondensation. Clogging may result in shutting down operation of thereaction chamber in order to clear the gas pathways, as well asexacerbate the particle formation that adversely affects the film formedin the chamber. In addition, changes to process conditions may affectthe deposition onto the wafer; for example, a change in temperature orpressure may lead to shifts in non-uniformities as it relates to filmproperties. These process shifts may lead to non-uniformities inthickness or concentration of the film, potentially resulting inscrapped wafers.

Prior art approaches to monitor concentrations of chemistries have beenlimited to temperatures less than 60-80° C. At these temperatures,condensation of gaseous precursors may occur, leading to the abovedescribed problems. An example of such a setup is described in thearticle entitled “Effluent Stream Monitoring of An Al2O3 Atomic LayerDeposition Process Using Optical Emission Spectroscopy,” by John P. Loo(available athttp://www.lightwindcorp.com/uploads/6/2/8/7/6282375/ald_effluent_monitoring_.pdf).

FIG. 1 illustrates a prior art optical emissions spectroscopy setup 10in an exhaust foreline. The optical emissions spectroscopy setup 10comprises a reaction chamber 20, an exhaust foreline 30, a sampler 40,an optical emission source 50, an optical emission spectrometer 60, anRF supply 70, and a processor 80. Exhaust from the reaction chamber 20travels through the exhaust foreline 30. The sampler 40 may take aportion of the exhaust in the exhaust foreline 30 and pass it throughthe optical emission source 50, which may be an inductively coupledplasma source. The optical spectrometer 60 and the RF supply 70 are ableto take readings of a spectrum generated in the optical emission source50 and provide a reading to the processor 80.

As a result, an apparatus and method to monitor concentrations ofchemical precursors in a high temperature environment is desired.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

While the specification concludes with claims particularly pointing outand distinctly claiming what are regarded as embodiments of theinvention, the advantages of embodiments of the disclosure may be morereadily ascertained from the description of certain examples of theembodiments of the disclosure when read in conjunction with theaccompanying drawing, in which:

FIG. 1 illustrates a prior art optical emissions spectroscopy approach;

FIG. 2 illustrates an exemplary reaction chamber in accordance with atleast one embodiment of the invention;

FIG. 3 illustrates a spectroscopy apparatus in accordance with at leastone embodiment of the invention;

FIGS. 4A-4C illustrate a spectroscopy apparatus in accordance with atleast one embodiment of the invention;

FIGS. 5A-5B illustrate an optical fiber apparatus in accordance with atleast one embodiment of the invention; and

FIG. 6 illustrates a multiple reaction chamber setup in accordance withat least one embodiment of the invention.

It will be appreciated that elements in the figures are illustrated forsimplicity and clarity and have not necessarily been drawn to scale. Forexample, the dimensions of some of the elements in the figures may beexaggerated relative to other elements to help improve understanding ofillustrated embodiments of the present disclosure.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Although certain embodiments and examples are disclosed below, it willbe understood by those in the art that the invention extends beyond thespecifically disclosed embodiments and/or uses of the invention andobvious modifications and equivalents thereof. Thus, it is intended thatthe scope of the invention disclosed should not be limited by theparticular disclosed embodiments described below.

As used herein, the term “substrate” may refer to any underlyingmaterial or materials that may be used, or upon which, a device, acircuit or a film may be formed.

As used herein, the term “chemical vapor deposition” (CVD) may refer toany process wherein a substrate is exposed to one or more volatileprecursors, which react and/or decompose on a substrate surface toproduce a desired deposition.

As used herein, the term “atomic layer deposition” (ALD) may refer to avapor deposition process in which deposition cycles, preferably aplurality of consecutive deposition cycles, are conducted in a processchamber. Typically, during each cycle the precursor is chemisorbed to adeposition surface (e.g., a substrate surface or a previously depositedunderlying surface such as material from a previous ALD cycle), forminga monolayer or sub-monolayer that does not readily react with additionalprecursor (i.e., a self-limiting reaction). Thereafter, if necessary, areactant (e.g., another precursor or reaction gas) may subsequently beintroduced into the process chamber for use in converting thechemisorbed precursor to the desired material on the deposition surface.Typically, this reactant is capable of further reaction with theprecursor. Further, purging steps may also be utilized during each cycleto remove excess precursor from the process chamber and/or remove excessreactant and/or reaction byproducts from the process chamber afterconversion of the chemisorbed precursor. Further, the term “atomic layerdeposition,” as used herein, is also meant to include processesdesignated by related terms such as, “chemical vapor atomic layerdeposition”, “atomic layer epitaxy” (ALE), molecular beam epitaxy (MBE),gas source MBE, or organometallic MBE, and chemical beam epitaxy whenperformed with alternating pulses of precursor composition(s), reactivegas, and purge (e.g., inert carrier) gas.

In the specification, it will be understood that the term “on” or “over”may be used to describe a relative location relationship, anotherelement or layer may be directly on the mentioned layer, or anotherlayer (an intermediate layer) or element may be intervened therebetween,or a layer may be disposed on a mentioned layer but not completely covera surface of the mentioned layer. Therefore, unless the term “directly”is separately used, the term “on” or “over” will be construed to be arelative concept. Similarly to this, it will be understood the term“under,” “underlying,” or “below” will be construed to be relativeconcepts.

Embodiments of the invention are directed to an apparatus and a methodfor monitoring or detecting a concentration of a chemical precursor thatenters a reaction chamber. Importance of such monitoring is due to thefact that such CVD and ALD processes may require strict chemicalconcentrations in order to form films of a particular composition andquality. It may be necessary to verify in real-time that an appropriateamount of the chemical precursor is being delivered with each pulse orflow. By such detection or monitoring, a variation in delivery ofprecursor to the wafers can be detected, and potentially, this couldavoid scrapping of wafers.

An Optical Emission Spectrometer (OES) may be used to verify the properamount of chemical precursor. An example of an OES may include the L3“Smart” Chemical Monitoring System manufactured by LightwindCorporation. Other OES may include the Sensor X system manufactured byPivotal Systems. An OES determines measures intensities along awavelength spectrum of a light emanating from a specimen. In this case,the specimen may be the chemical precursor. The intensities mayrepresent an amount of chemical precursor flowing through the OES.

FIG. 2 illustrates a reaction system 100 in accordance with at least oneembodiment of the invention. The reaction system 100 comprises areaction chamber 110; a gas source 120 for providing a gas reactant; ashowerhead 130 for distributing a gas; and a substrate holder 140 forholding a substrate 150 to be processed. The reaction system 100 alsoincludes a passageway 160 through which the gas reactant flows from thegas source 120 to the showerhead 130. The gas source 120 may provide aplasma gas source in at least one embodiment, or may provide a gasgenerated by a solid source precursor.

Prior approaches with implementing an OES into a reaction system havenot incorporated the OES directly between a solid source vessel and thereaction chamber. Embodiments in accordance with the invention mayperform a real-time monitoring of a vapor delivered from a solid sourcevessel into a reactor. Real-time monitoring may be to monitor a gasphase emission spectrum of each wafer, preferably after a few firstpulses when stability may be reached. Alternative embodiments may notmeasure an absolute concentration, but just detect for the presence of aparticular chemistry and perform a precursor sampling. With thisarrangement, an acceptable range of operation may be determined, withanything outside an error range resulting in fault detection.

In addition, embodiments may measure or detect concentrations ofparticular chemistries at the solid source vessel or on a foreline ofgas going towards the reaction chamber. Particular embodiments may allowfor obtaining better signals and readings compared to other embodimentsof the invention. A better signal may be obtained, but via an apparatussetup that may reduce the amount of precursor that enters into thereaction chamber, resulting in a higher cost to operate the reactionchamber.

Additional benefits obtained by embodiments of the invention may includean ability to match processes within more than one reaction chamber. AnOES may be used to ensure that each reaction chamber is receiving anacceptably matching does of chemistry. The OES may also determine ifcertain chemicals used in the film formation are present in anacceptable and repeatable amount for given process conditions.

FIG. 3 illustrates the gas source 120 in accordance with at least oneembodiment of the invention. The gas source 120 may be configured toperform a real-time concentration monitoring. The gas source 120comprises a heated vacuum enclosure 200, an RF source 220, an opticalemissions spectrometer 230, an exhaust pump 240, a flow restrictor 250,a valve 260A, a gas line 270A, a plurality of heaters 280A-280B, and anoptical fiber 300. The heated vacuum enclosure 200 comprises a solidsource vessel 210, a plurality of valves 260B-260C, and a gas line 270B.

The solid source vessel 210 may hold a solid precursor and convert itinto a gaseous precursor. The solid source vessel 210 may be a vesseldescribed in U.S. patent application Ser. No. 15/283,120, entitled“Reactant Vaporizer and Related Systems and Methods” and filed on Sep.30, 2016, or in U.S. patent application Ser. No. 15/585,540, entitled“Reactant Vaporizer and Related Systems and Methods” and filed on May 3,2017, both of which are incorporated by reference.

The gaseous precursor then travels from the solid source vessel 210through a valve 260C, and then can either go along a gas line 270B tothe passageway 160 or to the RF source 220 via a valve 260B. Themajority of the gaseous precursor goes to the passageway 160 andsubsequently the reaction chamber 110, where it will reach the surfaceof the wafer 150.

Of the gas that does not go to the reaction chamber 110, the RF source220 takes the draw of gaseous precursor and ionizes it. The RF sourcemay be an inductively coupled plasma source, a capacitively coupledplasma source, a microwave source, or a hot filament gas ionizer; anexample of such an RF source may include an ICP, manufactured byLightwand, for example. The optical emissions spectrometer 230 is ableto obtain a light spectrum of the ionized gaseous precursor in the RFsource 220 through the optical fiber 300. The optical emissionsspectrometer 230 may then monitor desired wavelengths in order todetermine whether there is an acceptable amount of gaseous precursor.The ionized gaseous precursor in the RF source 220 then passes throughthe flow restrictor 250 and a valve 260A to the exhaust pump 240 along agas line 270A.

In addition, the flow restrictor 250 may prevent an excess of gaseousprecursor from being sent to the exhaust pump 240, and thus, result inmore efficient use of the gaseous precursor. The flow restrictor 250 maycomprise a control orifice, a needle valve, or a fixed or variablerestrictor, for example. The heaters 280A-280B would provide heat to agaseous precursor diverted from the solid source vessel 210 to the RFsource 220, as well as the precursor traveling along the gas line 270B.The heating of the gaseous precursor primarily avoids condensation ofthe gaseous precursor.

FIG. 4A illustrates a gas source 120 in accordance with at least oneembodiment of the invention. The embodiment of the invention allows forflow of gas through the RF source rather than diffusion of gas into theRF source; this may result in a stronger spectrometer reading. The gassource 120 may detect a presence of a chemical in a setup allowing forprecursor sampling. The gas source 120 comprises a heated vacuumenclosure 200. The heated vacuum enclosure 200 comprises a solid sourcevessel 210, a plurality of valves 260B-260F, a gas line 270B, a flowrestrictor 290, and an inert gas source 310. Gas from the inert gassource 310 travels in the gas line 270 a through the valve 260 b intothe solid source vessel 210, where it carries a gaseous precursor formedfrom a solid precursor. The resulting gaseous precursor travels throughthe valves 260D-260E and may either go to the reaction chamber 160 or besampled by going through valve 260F and the flow restrictor 290. Thevalve 260C serves as a bypass valve in isolating the solid source vessel210.

The gas source 120 also comprises an RF source 220, an optical emissionsspectrometer 230, an exhaust pump 240, a flow restrictor 250, a valve260A, a plurality of heaters 280A-280B, a gas line 270 b, and an opticalfiber 300. The heater 280A heats exhaust gas within the gas line 270A,while the heater 280B heats the portion of the gas line 270B disposedbetween the vacuum enclosure 200 and the RF source.

FIG. 4B illustrates a gas source 120 in accordance with at least oneembodiment of the invention. The gas source 120 is similar to thatillustrated in FIG. 4A as it also is capable of performing a periodicdetection of a chemical concentration. A gas line 270 c is split from agas line 270 b, while a heater 280 heats the gas line outside of avacuum enclosure 200 up to an RF source 220 and a valve 260 a.

An optical fiber 300 may obtain a light spectrum signal from the RFsource 220 and provide it to an optical emissions spectrometer 230. Thearrangement of the RF source 220 and the optical fiber 300 may avoiddeposition of a film on a window attached to the optical fiber 300. Inaddition, build-up of a precursor may be avoided within a vacuum exhaustthat travels through the valve 260 a and a pump 240 along the gas line270 c.

FIG. 4C illustrates a gas source 120 in accordance with at least oneembodiment of the invention. The gas source 120 is similar to thatillustrated in FIG. 4A, with the main difference in that a valve 260F isdisposed between a gas line having a valve 260D and a valve 260E, whilein FIG. 4A, the valve 260F is disposed in the gas line after the valve260E. In other words, the valve 260F is upstream of the valve 260E inFIG. 4C, while it is disposed downstream of the valve 260E in FIG. 4A.The embodiment illustrated in FIG. 4C may sample the gaseous precursorbetween processing of wafers or front opening unified pods (FOUPs)rather than real time monitoring.

FIGS. 5A-5B illustrate an optical fiber 300 in accordance with at leastone embodiment of the invention. FIG. 5A illustrates an end view of theoptical fiber 300, while FIG. 5B illustrates a cross-sectional view ofthe optical fiber 300. The optical fiber 300 comprises a lighttransmission section 310, a purge gas channel 320, and ahigh-temperature outer sheath 330. The optical fiber 300 also comprisesa wide view fiber optic 340 attached to the light transmission section310 and a purge nozzle 350 attached to the high-temperature outer sheath330. The purge nozzle 350, along with a purge gas traveling through thepurge gas channel 320, may allow for reducing or minimizing build-up ofa film formed on the wide view fiber optic 340. The optical fiber 300may be useful for monitoring within a foreline disposed proximate to agas source.

FIG. 6 illustrates a multiple reaction chamber setup 400 in accordancewith at least one embodiment of the invention. The multiple reactionchamber setup 400 allows for a matching of the process in multiplechambers, and comprises: a first reaction chamber 410A, a secondreaction chamber 410B, a first gas source 420A, a second gas source420B, a first sampling port 430A, a second sampling port 430B, a firstvalve 440A, a second valve 440B, a first gas line 450A, a second gasline 450B, a RF source/OES device 460, an exhaust line 470, and anexhaust pump 480.

The first gas source 420A and the second gas source 420B may beconfigured to provide a same gaseous precursor to the first reactionchamber 410A and the second reaction chamber 410B. The first samplingport 430A may be configured to sample a gas within the first reactionchamber 410A. In an alternative embodiment, the first sampling port 430Amay be configured to be between the first gas source 420A and the firstreaction chamber 410A. Similarly, the second sampling port 430B may beconfigured to sample a gas within the second reaction chamber 410B. Inan alternative embodiment, the second sampling port 430B may beconfigured to be between the second gas source 420B and the secondreaction chamber 410B.

The first valve 440A and the second valve 440B may be configured torestrict the amount of gas that leaves the first reaction chamber 410Aand the second reaction chamber 410B and into the first gas line 450Aand the second gas line 450B, respectively. The first valve 440A and thesecond valve 440B may comprise a needle valve, a fixed flow restrictor,or a variable flow restrictor, for example. The first gas line 450A andthe second gas line 450B may feed into the RF source/OES 460; in analternative embodiment, there may be separate RF source/OES setups foreach of the first gas line 450A and the second gas line 450B. The RFsource/OES 460 may perform a gas ionization and a spectrometry readingin a manner described previously on the gaseous precursor, beforesending the gas to the exhaust pump 480 via the exhaust line 470.

The example embodiments of the disclosure described above do not limitthe scope of the invention, since these embodiments are merely examplesof the embodiments of the invention, which is defined by the appendedclaims and their legal equivalents. Any equivalent embodiments areintended to be within the scope of this invention. Indeed, variousmodifications of the disclosure, in addition to those shown anddescribed herein, such as alternative useful combination of the elementsdescribed, may become apparent to those skilled in the art from thedescription. Such modifications and embodiments are also intended tofall within the scope of the appended claims.

What is claimed is:
 1. A device for monitoring a concentration of a gassource comprising: a solid source vessel, the solid source vesselcontaining a solid precursor and sublimating the solid precursor into afirst gas precursor; a gas line coupled to the solid source vessel, thegas line configured to move a first portion of the first gas precursorinto a reaction chamber and move a second portion of the first gasprecursor into a sampling port; a RF source coupled to the samplingport, the RF source ionizing the first gas precursor; an opticalemissions spectrometer coupled to the RF source, the optical emissionsspectrometer configured to obtain a light spectrum of the ionized firstgas precursor; and an exhaust pump coupled to the RF source andconfigured to exhaust the ionized first gas precursor; wherein aconcentration of the ionized first gas precursor is determined based onthe light spectrum.
 2. The device of claim 1, further comprising aheater to heat a part of the gas line connected to the RF source.
 3. Thedevice of claim 1, further comprising a plurality of valves to control aflow of the first gas precursor from the solid source vessel.
 4. Thedevice of claim 1, wherein the RF source comprises at least one of: aninductively coupled plasma source; a capacitively coupled plasma source;a microwave source; or a hot filament gas ionizer.
 5. The device ofclaim 1, further comprising a flow restrictor disposed between the RFsource and the exhaust pump.
 6. The device of claim 1, furthercomprising an optical fiber coupling the RF source to the opticalemissions spectrometer.
 7. The device of claim 6, wherein the opticalfiber comprises: a light transmission section; a purge gas channel; anouter sheath; a wide view fiber optic attached to the light transmissionsection; and a purge nozzle attached to the outer sheath.
 8. The deviceof claim 1, further comprising a heated vacuum enclosure to hold atleast the solid source vessel.
 9. The device of claim 8, furthercomprising a flow restrictor within the heated vacuum enclosure.
 10. Thedevice of claim 1, further comprising an inert gas source configured toprovide an inert carrier gas for the first gas precursor.
 11. Anapparatus for depositing a film on a semiconductor wafer comprising: afirst reaction chamber configured to hold a first semiconductor wafer; afirst gas source configured to provide a first gas precursor to thefirst reaction chamber; a second gas source configured to provide asecond gas precursor to the first reaction chamber, the second gassource comprising a first solid source vessel, the first solid sourcevessel containing a solid precursor and sublimating the solid precursorinto the second gas precursor; a first gas line coupled to the firstsolid source vessel, the first gas line configured to move a firstportion of the second gas precursor into the first reaction chamber andmove a second portion of the second gas precursor into a first samplingport; a RF source coupled to the first sampling port, the RF sourceionizing the second gas precursor; an optical emissions spectrometercoupled to the RF source, the optical emissions spectrometer configuredto obtain a light spectrum of the ionized second gas precursor; and anexhaust pump coupled to the RF source and configured to exhaust theionized second gas precursor; wherein a concentration of the ionizedsecond gas precursor is determined based on the light spectrum.
 12. Theapparatus of claim 11, wherein the RF source comprises at least one of:an inductively coupled plasma source; a capacitively coupled plasmasource; a microwave source; or a hot filament gas ionizer.
 13. Theapparatus of claim 11, further comprising a flow restrictor disposedbetween the RF source and the exhaust pump.
 14. The apparatus of claim11, further comprising an optical fiber coupling the RF source to theoptical emissions spectrometer.
 15. The apparatus of claim 14, whereinthe optical fiber comprises: a light transmission section; a purge gaschannel; an outer sheath; a wide view fiber optic attached to the lighttransmission section; and a purge nozzle attached to the outer sheath.16. The apparatus of claim 11, further comprising: a second reactionchamber configured to hold a second semiconductor wafer; a third gassource configured to provide a third gas precursor to the secondreaction chamber; a fourth gas source configured to provide a fourth gasprecursor to the second reaction chamber, the second gas sourcecomprising a second solid source vessel, the second solid source vesselcontaining a second solid precursor and sublimating the second solidprecursor into the fourth gas precursor; and a second gas line coupledto the second solid source vessel, the second gas line configured tomove a first portion of the fourth gas precursor into the secondreaction chamber and move a second portion of the fourth gas precursorinto a second sampling port; wherein the RF source is coupled to thesecond sampling port and ionizes the fourth gas precursor; and whereinthe optical emissions spectrometer couples to the RF source and isconfigured to obtain a light spectrum of the ionized fourth gasprecursor.
 17. The apparatus of claim 11, further comprising a firstinert gas source configured to provide an inert carrier gas for thefirst gas precursor.
 18. The apparatus of claim 11, further comprising aheated vacuum enclosure to hold at least the first solid source vessel.